Lorenzo De Medici Sweat (May 26, 1818 – July 26, 1898) was a U.S. Representative from Maine.
He was born in Parsonsfield, Maine, where he attended Parsonsfield Seminary, a Freewill Baptist school. Sweat then attended Bowdoin College, from where he graduated in 1837. He graduated from Harvard University in 1840, having studied law, and began to practice law in New Orleans. After this, he returned to Maine and settled in Portland, Maine. He married Margaret Jane Mussey in 1849. Sweat held various local offices including that of the Portland city solicitor from 1856 to 1860. He served as a member of the State Senate in 1862, and was elected as a Democrat to the Thirty-eighth Congress and served from March 4, 1863, to March 3, 1865, when he was defeated for re-election to the Thirty-ninth Congress. He was later defeated for election to the Fortieth Congress.
He later was a delegate to the Union National Convention held in Philadelphia in 1868, and to the 1872 Democratic National Convention, where he was chosen as a member of the Democratic National Committee and served for four years until 1876.
He was an honorary commissioner to the World's Exposition in Paris in 1867 and that in Vienna in 1873.
The Portland house he lived in, the McLellan-Sweat Mansion, later became the Portland Museum of Art, following a bequest by his wife. Today it is a National Historic Landmark.
His body is interred in Evergreen Cemetery in Portland, Maine.